Heat exchanger

ABSTRACT

A heat exchanger has tubes arranged in parallel at regular distances so they extend in the same direction as the ventilation direction of heat exchange medium flowing through the tube. The heat exchange medium is introduced and distributed to the plural tubes via an inlet tank. A fin interposed between the tubes increases the contact surface area of air passing between the tubes. The heat exchange medium flowing through the tubes is collected and then discharged by an outlet tank. The dimensions of the cross-sectional area S tube  of the tube and the sectional area S tank  of the inlet tank or the outlet tank satisfy the following formula: 
     
       
         
           
             0.04 
             &lt; 
             
               
                 sectional 
                  
                 
                     
                 
                  
                 area 
                  
                 
                     
                 
                  
                 of 
                  
                 
                     
                 
                  
                 tube 
                  
                 
                     
                 
                  
                 
                   ( 
                   
                     S 
                     tube 
                   
                   ) 
                 
               
               
                 sectional 
                  
                 
                     
                 
                  
                 area 
                  
                 
                     
                 
                  
                 of 
                  
                 
                     
                 
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                 tank 
                  
                 
                     
                 
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                   ( 
                   
                     S 
                     tank 
                   
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             &lt; 
             0.06

TECHNICAL FIELD

The present invention relates to a heat exchanger, more particularly, toa heat exchanger which improves shapes and sizes of a tube and a tank soas to increase a heat radiation performance.

BACKGROUND ART

FIG. 1 is a view showing a general cooling and heating system of avehicle. In a vehicle engine 1, high temperature and high pressure gasis ignited and burned. Therefore, if leaving the vehicle engine 1 as itis, it will be overheated and a metallic material used in constructingthe engine 1 is melted and thus a cylinder, a piston and the like may bedamaged seriously. To prevent such damage, as shown in FIG. 1, a waterjacket (not shown) in which cooling water is stored is formed around thecylinder of the vehicle engine 1 and the cooling water is circulatedthrough a radiator 2 or a heater core 3 by a water pump 5 so as to coolthe engine 1. The cooling water may be not passed through the heatercore 3, but directly returned to the water jacket through a bypasscircuit 6 according to the purpose of heating and cooling. At this time,a thermostat 4 is provided in a passage for the cooling water so as tofunction as a control device for preventing the overheating of theengine 1 by controlling an opening/closing degree of the passage on thebasis of a temperature of the cooling water.

The radiator 2 is a kind of heat exchanger for radiating heat of thecooling water which is heated by heat of the engine 1 while beingcirculated in the engine 1. The radiator 2 is disposed in an engine roomof the vehicle and provided with a cooling fan at a center portionthereof so as to cool a radiator core. Further, the heater core 3 is apart of an air conditioner of the vehicle and also functions as the kindof heat exchanger for supplying warm air to an inside of the vehicleusing the high temperature cooling water which absorbs the heatgenerated from the engine 1 while being circulated in the engine 1. Inthe heater core 3, the high temperature cooling water which is heated bythe heat of the engine 1 is passed through a fin and a tube of theheater core 3 so as to transfer the heat to air supplied from theoutside, thereby providing the warm air to the inside of the vehicle.

In order to properly heat the inside of the vehicle, a heat exchangeperformance of the heater core should be increased. therefore, in orderfor the heat exchange to be generated more smoothly, many efforts havebeen made by varying dimensions and shapes of the tube and tankconstructing the heat exchanger using a basic principle that a contactsurface for the heat exchange should be increased so that the heatexchange is performed smoothly, thereby increasing the heat exchangeperformance. In addition, the heat exchanger is made of a materialhaving a high heat conductivity which can rapidly transfer the heatbetween the heat exchange medium in the heat exchanger and an outermedium passing the outside of the heat exchanger, thereby increasing theheat exchange performance. The varying of the dimensions, shapes andmaterials of each part is to basically increase a heat exchangecoefficient which is directly associated with the heat exchangeperformance. As described above, if the surface area of each part isincreased, the heat exchange performance is also increased. However,since there is a limitation on a space for installing the heatexchanger, it is very difficult to largely increase the surface area inthe limited volume. Furthermore, in case of increasing the contactsurface area for the heat exchange as described above, particularly, incase of the tube in which the heat exchange medium is accommodated, asectional area of a passage for the heat exchange medium becomesreduced. If the sectional area of the passage is reduced, a flow rate ofthe heat exchange medium is increased and a pressure thereof is dropped,and thus the heat exchange coefficient is increased. However, if thesectional area of the passage is reduced excessively, the pressure isalso dropped excessively and thus the heat exchange coefficient isreduced. Therefore, it is difficult to optimize the heat exchangeperformance only by reducing the sectional area of the passage.

DISCLOSURE Technical Problem

An object of the present invention is to provide a heat exchanger whichdeduces a relationship between the varying of dimensions relevant tofluid flowing in the header tank and heat exchange tube and the heatexchange performance according to the change of distributed fluidflowing and thus improves the dimensions and shapes of the tank andtube, thereby optimizing the heat exchange performance.

Technical Solution

In order to achieve the above objects, there is provided a heatexchanger comprising heat exchanger 100 comprising a plurality of tubes20 which are arranged in parallel at regular distances to be parallelwith a ventilation direction and through which a heat exchange medium isflowed; an inlet tank 11 in which the heat exchange medium is introducedand then distributed to the plurality of tubes 20; a fin 30 which isinterposed between the tubes 13 so as to increase a contact surface withair passing between the tubes 20; and an outlet tank 12 in which theheat exchange medium flowed through the tubes 20 is collected and thendischarged, wherein dimensions of the sectional area S_(tube) of thetube 20 and the sectional area S_(tank) of the inlet tank 11 or theoutlet tank 12 satisfy a following formula:

$0.04 < \frac{{sectional}\mspace{14mu} {area}\mspace{14mu} {of}\mspace{14mu} {tube}\mspace{14mu} \left( S_{tube} \right)}{{sectional}\mspace{14mu} {area}\mspace{14mu} {of}\mspace{14mu} {tank}\mspace{14mu} \left( S_{tank} \right)} < 0.06$

Preferably, a volume V_(tank) of the inlet tank 11 or the outlet tank 12and a total sectional area A_(tube) of the tubes 20 calculated bymultiplying the sectional area of the tube 20 and the number of tubes 20satisfy a following formula:

$150 < \frac{{{volume}\mspace{14mu} {of}\mspace{14mu} {inlet}\mspace{14mu} {tank}\mspace{14mu} {or}\mspace{14mu} {outlet}\mspace{14mu} {tank}\mspace{14mu} \left( V_{tank} \right)}\mspace{11mu}}{{total}\mspace{14mu} {sectional}\mspace{14mu} {area}\mspace{14mu} {of}\mspace{14mu} {tubes}\mspace{14mu} \left( A_{tube} \right)} < 230$

ADVANTAGEOUS EFFECTS

According to a heat exchanger of the present invention, it is possibleto deduce a relationship between the varying of dimensions relevant tofluid flowing in the header tank and heat exchange tube and the heatexchange performance according to the change of distributed fluidflowing and thus improves the dimensions and shapes of the tank andtube, thereby optimizing the heat exchange performance. Furthermore, itis possible to easily design the heat exchanger having the optimal heatexchange performance, thereby saving labor, cost, time and the like.

DESCRIPTION OF DRAWINGS

The above and other objects, features and advantages of the presentinvention will become apparent from the following description ofpreferred embodiments given in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a view showing a general cooling and heating system of avehicle.

FIG. 2 is a perspective view of a heat exchanger.

FIG. 3 is a cross-sectional view of a tank of the heat exchanger.

FIG. 4 is a cross-sectional view of a tube of the heat exchanger.

FIG. 5 is a view showing a length of the tank and an effective area inthe heat exchanger.

FIG. 6 is a graph showing a heat exchange performance per effective areawith respect to each factor.

[Detailed Description of Main Elements] 100: heat exchanger 10: tank 11: inlet tank 12: outlet tank  20: tube 30: fin

BEST MODE

Hereinafter, the embodiments of the present invention will be describedin detail with reference to accompanying drawings.

FIG. 2 is a perspective view of a heat exchanger 100. A heat exchangemedium is flown in the heat exchanger 100, and the heat exchanger 100includes a plurality of tubes 20 which are arranged in parallel atregular distances to be parallel with a ventilation direction, and tanks10 which are respectively coupled to both ends of the tubes 20. Thetanks 10 are divided into an inlet tank 11 in which the heat exchangemedium is introduced and then distributed to the plurality of tubes 20and an outlet tank 12 in which the heat exchange medium moved throughthe tubes 20 is collected and then discharged. Fins 30 are providedbetween the tubes 20 so as to increase a contact surface area with airflowing between the tubes 20. As described above, the heat exchangemedium is introduced through an inlet port of the inlet tank 11,collected in the outlet tank 12 through the tubes 20 and then dischargedthrough an outlet port of the outlet tank 12. While the heat exchangemedium is flowed through the tubes 20, heat exchange is occurred betweenthe heat exchange medium received in the tubes 20 and the external airthrough the tubes 20 and the fins 30 interposed between the tubes 20. Inother words, the heat exchange is occurred at the tubes 20 and fins 30s,particularly, at an area where the tubes 20 is contacted with the air.Thus, the shapes and dimensions of the heat exchanger 100 greatly exertan influence on the entire heat exchange performance.

As described in the conventional heat exchanger, although the optimaldimension and shape of each tank 10 and tube 20 are obtained, the heatexchange performance of the heat exchanger 100 which is formed bycoupling of each tank 10 and tube 20 is not optimized. As describedabove, since the heat exchange medium is introduced into the tank 10 andthen flowed through the tube 20, each dimension and shape of the tanks10 and tubes 20 has the specific relationship.

Hereinafter, the heat exchange phenomenon occurred in the heat exchangerwill be described briefly. First of all, the heat exchange is occurredby convection between the heat exchange medium in the tubes 20 and innersurfaces of the tubes 20, and the heat is transferred from the innersurfaces of the tubes 20 to outer surfaces of the tubes 20 and the fins30. Finally, the heat exchange is occurred between the outer surfaces ofthe tubes 20 and the fins 30 and the external air by the convection. Asdescribed above, the heat exchange phenomenon occurred in the heatexchanger depends on the convective heat exchange, and a heat exchangeamount also depends on the contact surface area and flow rate. In theaspect of the contact surface area, the larger the surface area of thetube 20 and fin 30 contacted with the external air becomes, the better.And in the aspect of the flow rate, the larger the flow rate of the heatexchange medium flowing into the tube 20 becomes, the better.

FIGS. 3 and 4 are views showing each factor having an influence on theheat exchange, wherein S_(tank) is a surface area of FIG. 3, i.e., asectional area of a passage in the tank 10, and S_(tube) is a surfacearea of FIG. 4, i.e., a sectional area of a passage of the tube 20. Asshown in FIGS. 3 and 4, the S_(tube) is typically smaller than thesectional area of the passage in the tank 10, and due to the reductionof the sectional area of the passage, the flow rate is increased whilethe heat exchange medium is flowed from the tank 10 to the tube 20.Since the flow rate is directly related with a pressure upon the flowingof the fluid, an amount of pressure drop is also increased according asa difference between the sectional areas of passages of the tank 10 andthe tube 20 is increased. In other words, it will be understood that, asthe difference between the sectional areas of passages of the tank 10and the tube 20 is increased, the flow rate is increased, and thus theheat exchange performance is increased. However, in case that thedifference between the sectional areas is increased excessively, theheat exchange medium can not be flowed smoothly. And as the amount ofpressure drop is increased excessively, the heat exchange performance isdeteriorated.

In the heat exchanger 100, the factors of the tank 10 and tube 20, whichdirectly exert an influence on the heat exchange performance pereffective surface area and show a specific correlation with each other,is expressed as follows:

$\begin{matrix}{\frac{S_{tube}}{S_{tank}},\frac{V_{tank}}{A_{tube}}} & \left\lbrack {{Formula}\mspace{14mu} 1} \right\rbrack\end{matrix}$

In the formula 1, S_(tank) is the sectional area of the passage of thetank 10 shown in FIG. 3, S_(tube) is the sectional area of the passageof the tube 20 shown in FIG. 4, V_(tank) is a volume of the tank 10, andA_(tube) is a total sectional area of the tubes 20. Further, the volumeV_(tank) can be obtained by multiplying a length l_(tank) of the tank 10by the sectional area S_(tank) of the passage of the tank 10, and thetotal sectional area A_(tube) can be obtained by multiplying eachsectional area S_(tank) of the passage of the tube 20 by the number N oftubes. A formula 2 to be expressed blow shows a relationship between thefactors.

V _(tank) =l _(tank) ×S _(tank)

A _(tube) =N×>S _(tube)  [Formula 2]

Since the actual heat exchange is performed between the heat exchangemedium in the tube 20 and the external air while the external air passesbetween the tubes 20, the heat exchange is substantially performed atthe surface area of the tube 20 and the fin 30 perpendicular to aflowing direction of the external air. This surface area is theeffective surface area S_(eff) as shown in FIG. 5. In order to expressthe heat exchange performance regardless of a size of the heatexchanger, a valuation of the heat exchange performance is obtained byonly the effective surface area S_(eff). Assuming that the heat exchangeamount which is substantially generated is Q, the heat exchange amountQ_(Ae) per effective surface area is expressed as follows:

$\begin{matrix}{Q_{Ae} = \frac{Q}{S_{eff}}} & \left\lbrack {{Formula}\mspace{14mu} 3} \right\rbrack\end{matrix}$

Since the present invention provides a dimension relationship betweenthe tank 10 and the tube 20 capable of maximizing the heat exchangeperformance per effective surface area, the heat exchange performanceper effective surface area is estimated on the basis of the heatexchange amount Q₀ per effective surface area which is a requirement ina vehicle. The heat exchange performance η per effective surface area isexpressed as follows:

$\begin{matrix}{\eta = \frac{Q_{Ae}}{Q_{0}}} & \left\lbrack {{Formula}\mspace{14mu} 4} \right\rbrack\end{matrix}$

FIG. 6 is a graph showing the heat exchange performance η per effectivearea with respect to each factor, wherein FIG. 6 a shows a change of ηwith respect to S_(tube)/S_(tank) and FIG. 6 b shows a change of η withrespect to V_(tank)/A_(tube), wherein an area unit is cm², a volume unitis cm³ and a thermal unit is kcal/hr. As shown in the drawing, the heatexchange performance η is gradually increased and then reduced from apeak point. In other words, the heat exchange coefficient is increased,according as the difference between the sectional areas of passages isincreased, and then the heat exchange coefficient is reduced due to theincrease in the amount of pressure drop after the difference between thesectional areas of passages a certain point. Referring to the graph ofFIG. 6 a, when the value of S_(tube)/S_(tank) is 0.04˜0.06, the heatexchange performance η per effective surface area is optimized.Therefore, from this it is possible to deduce the relationship betweenthe dimensions of the single tube and tank so as to optimize the heatexchange performance η per effective surface area.

Further, as shown in FIG. 6 b, with respect to V_(tank)/A_(tube), theheat exchange performance η is also increased gradually and then reducedfrom a peak point. In other words, as shown in FIG. 6 b, when the valueof V_(tank)/A_(tube) is 150˜230, the heat exchange performance η pereffective surface area is optimized. The graph of FIG. 6 a shows therelationship between the dimensions of each tube and tank, and the graphof FIG. 6 b shows the relationship between the dimensions of the entiretubes and tanks. Thus, it is possible to deduce the relationship betweenthe dimensions in the entire heat exchanger referring to the graphs.

Those skilled in the art will appreciate that the conceptions andspecific embodiments disclosed in the foregoing description may bereadily utilized as a basis for modifying or designing other embodimentsfor carrying out the same purposes of the present invention. Thoseskilled in the art will also appreciate that such equivalent embodimentsdo not depart from the spirit and scope of the invention as set forth inthe appended claims.

INDUSTRIAL APPLICABILITY

According to a heat exchanger of the present invention, it is possibleto deduce a relationship between the varying of dimensions relevant tofluid flowing in the header tank and heat exchange tube and the heatexchange performance according to the change of distributed fluidflowing and thus improves the dimensions and shapes of the tank andtube, thereby optimizing the heat exchange performance. Furthermore, itis possible to easily design the heat exchanger having the optimal heatexchange performance, thereby saving labor, cost, time and the like.

1. A heat exchanger, comprising: a plurality of tubes arranged (a) inparallel at regular distances to be extend in a ventilation directionsand (b) so a heat exchange medium is adapted to flow through them; aninlet tank into which the heat exchange medium is adapted to beintroduced and then distributed to the plurality of tubes; a fininterposed between the tubes for increasing the contact surface of thetubes with air passing between the tubes; and an outlet tank forcollecting and then discharging the heat exchange medium which isadapted to flow through the tube wherein dimensions of thecross-sectional area S_(tube) of the tube and the cross-sectional areaS_(tank) of the inlet tank or the outlet tank are in accordance with:$0.04 < \frac{{sectional}\mspace{14mu} {area}\mspace{14mu} {of}\mspace{14mu} {tube}\mspace{14mu} \left( S_{tube} \right)}{{sectional}\mspace{14mu} {area}\mspace{14mu} {of}\mspace{14mu} {tank}\mspace{14mu} \left( S_{tank} \right)} < 0.06$2. The heat exchanger according to claim 1, wherein the volume V_(tank)of the inlet tank or the outlet tank and the total cross-sectional areaA_(tube) of the tubes calculated by multiplying the sectional area ofthe tube and the number of tubes are in accordance with:$150 < \frac{{{volume}\mspace{14mu} {of}\mspace{14mu} {inlet}\mspace{14mu} {tank}\mspace{14mu} {or}\mspace{14mu} {outlet}\mspace{14mu} {tank}\mspace{14mu} \left( V_{tank} \right)}\mspace{11mu}}{{total}\mspace{14mu} {sectional}\mspace{14mu} {area}\mspace{14mu} {of}\mspace{14mu} {tubes}\mspace{14mu} \left( A_{tube} \right)} < 230$